The invention relates to a process for producing feed spools for a twisting operation in which two slivers are first drafted, are then prestrengthened by means of pneumatic false-twisting and are then wound onto feed spools while they are located next to one another, as well as to an arrangement for producing such wound feed spools.
By means of the known processes and arrangements of the initially mentioned type (See European Patent Applications EP-A Nos. 38 143, 70 210), a significant increase in production can be achieved because the slivers are first prestrengthened only by the pneumatic false-twisting without reaching a strength that will make them suitable for a further processing as a single yarn. The final strength is obtained only by means of a subsequent twisting operation. However, the yarns that are only prestrengthened, particularly in the area behind the devices for pneumatic false-twisting, are subjected to considerable stress, so that yarn breakages occur frequently. It is therefore known to reinforce the slivers by means of filament yarn. For this purpose, a filament yarn is added to each of these slivers at the pair of delivery rollers of the pertaining drafting frame. Filament yarn of this type, however, is relatively expensive so that at least some of the advantages that are obtained by the simplified spinning and twisting process are eliminated again.
An objective of the invention is to provide a process and arrangement which minimizes the occurrence of yarn breakages with less expenditures.
This objective is achieved by adding a filament yarn after the pneumatic false-twisting and before the winding-up of the false twisted yarn.
In the case of the invention, only one filament yarn is required. In this case, the invention is based on the recognition that the false twist that is applied during the pneumatic false twisting acts as a protecting twist until the drafting frame is reached so that in this area the danger of a yarn breakage is relatively low. The critical range will therefore be behind the devices for the pneumatic false twisting, because the false twist opens up and only the prestrengthening is in effect that is produced by a residual winding-around of the edge fibers. According to the recognition of the invention, it is therefore sufficient to add the filament yarn not before this point at which the two yarn components are guided together so that the prestrengthened slivers and the filament yarn jointly pass through the withdrawal device and the wind-up device. The filament yarn therefore offers an improved protection against yarn breakages particularly in the area of the wind-up device in which, because of the side traverse motion, the stress to the yarn is increased.
In a further development of preferred embodiments of the invention, it is provided that the filament yarn is fed between the slivers that, during the winding-up, embed the filament yarn between themselves. During the subsequent twisting-together, a new type of core twist yarn is obtained.
In a further development of preferred embodiments of the invention, it is provided that the filament yarn is fed under a defined, preferably adjustable, tension. As a result, it is possible to coordinate the filament yarn, with respect to the feeding, with the prestrengthened slivers leaving the false-twisting devices.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.